Process of manufacturing sheet material and product obtained thereby



Patented Jan. 5, 1932 UNITED STATES PATENT OFFICE REED P. ROSE, OF JACKSON HEIGHTS, NEW YORK, AND HAROLD E. CUDE, OF SOUTH MANGHESTER, CONNECTICUT, ASSIGNORS TO GENERAL RUBBER COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY 6 PROCESS OF'MANUFAGTURING SHEET MATERIAL AND PRODUCT OBTAINED THEREBY No Drawing. Application filed May 31,

This invention relates to the preparation of rubber treated fibrous compounds which can be formed into sheets on a paper machine or molded into specific products.

Rubber has been added to paper pulp in varying percentages which may be as great as 40-100% of the weight of the pulp, although in general the amount of rubber has not often exceeded -20%. When, however, 1, more than this latter percentage of rubber is incorporated with the pulp'and formed into paper, the product'may vary within much greater limits lie ending upon the nature of the pulp, the kind of pulp, the method of cooking and the paper making operations. It will be observed, however, that as the amount of rubber is increased above 1020%, the product beginsvto assume the properties of a rubber compounded with paper pulp rather than those of ordinary paper as the term is generally understood.

7 By varying the methodsof cooking the pulp or the beating process or both, but employing the same kind of raw material and the same percentages of rubber, itis possible to prepare rubber-containing sheet materials having strength and other properties, such as pliability andthe like, equal to those of. woven fabric. The products may have properties intermediate those of ordinary papers containing say 10-20% of rubber or less and rubber compounds ,made according to the ordinary manufacturing processes in the rubber industry. The distincand sheets made by the usual rubbercompounding practice is mainly that the former can be manufactured on the standard types of paper machines and can therefore be made in larger sizes and more economically than rubber sheets can be prepared by the calendaring operation employed in the rubber industry. The present invention is con "cerned with the manufacture of'rubber-containing sheets by paper making methods.-

Accordingly, an object of the present invention is to provide a rubber-containing brous materia having a high resistance to ed fibrous sheet material having a highly tion between fibrous sheets containing rubber Another object is to prepare a rub- 1928. Serial No. 282,043.

ber-containing fibrous material having good wearing qualities, high tear and abrasion resistance, and high flexibility.

Without desiring to place undue limitations upon the scopeof the invention beyond what may be required by the prior art, the invention consists in cooking cotton or other paper making fibres, beating them into a paper-making stuff. combining rubber therewith, and forming into sheet material. The invention also contemplates forming the rubber-pulp mixture into predetermined shapes.

Cotton fibres are preferred as the raw material for these improved papers and sheets but other paper making fibresincluding vegetable fibres may also be used. But to gain the full advantage of the invention, it is first the previous methods,.while entirely satisfactory for paper manufacturing purposes, are not at all suitable in the present invention, for these methods invariably destroy the strength of the fibres, and particularly the resistance to tear is affected. Raw cotton linter or any kind of cotton fibres may be employed as the fibre. Cotton rags or cotton waste may be utilized, but it is preferred to use raw cotton fibre or new rags or waste, rather than old material. Waste fibre, such as rags and the like which has previously been cooked to remove the wax, etc., may be mixed with raw cotton fibres, if desired, or with wood pulp'or other paper making fibre. Incarrying out the invention, 2700 lbs. of raw cotton linter are cookedwith 342 lbs. of 58% soda ash (from 5 to 9% on the raw linter) in the presence of 5000 gallons of water. The final concentration of the cooking liquor should not be higher than 2%. The cooking can be done in any of the wellknown cookers. In this specific illustration a horizontal rotary cooker is used. The cooking is carried out at approximately 230 F. or at a maximum steam pressure of approximately 5 lbs. per sq. inch, the length of time being 1 hrs. The temperature during the first 40 min. of the cooking does not exceed 120 F. It appears essential that the temperature should not be allowed to become too high. With the steam pressure given above, the time limit for the cooking should not exceed 3 hrs. The liquor is drained out of the cooker and the latter is filled with clean water and agitated for say hr. to wash out the soda. The washing may be carried out just as satisfactorily in a'beater washer. An hours washing in the beater is usually sufficient. The extent to which the waxes, etc. are removed will of course depend somewhat upon the nature of the product desired. While in general the use of an alkali carbonate is preferred, caustic soda or other equivalent material may be used if the dilution and other operating conditions are properly controlled so as to prevent too severe action on the fibre.

The fibre, cleansed of the fats, wax, etc., is

, now beaten. preparatory to making paper.

With the cooking given above and with the type of raw material, 1% hrs. is a sufficient time for the beating if a very efficient high speed beater is used. It is pointed out, however, that the beating time may vary with different types of heaters and may be short ened or increased depending on the type of the product desired. The beating is done in conformance with standard practice. The invention is not limited to the proportions given above, for these may be varied to meet special requirements without departing from the spirit of the invention.

The beaten fibre may then be combined with 675 lbs. of rubber in the form of rubber latex, which proportion gives approximately 20% of rubber on the finished paper. The latex is added after the pulp has been beaten, and is added directly to the beater after the roll has been raised off the bed plate, the contents of the beater having previously been made alkaline with ammonla or its equivalent. The heater roll is then revolved for a period of time in order to mix the rubber latex with the beaten pulp. The rubber is then deposited from the latex upon the fibres by adding about of the quantity of coagulant necessary to cause complete coagulation. The mixing is continued and the rubberis thereupon agglomerated upon the fibres. The remainder of the coagulant is then added and the agglomerated rubber is coagulated upon the fibres. With the above amount of fibre, a suitable quantity of coagulant is 50 lbs. of paper makers alum. This is dissolved and of it added to produce agglomeration and the remainder is added subsequently in an amount suflicient to give the contents of the beater an acid reaction to litmus. If desired a protective colloid such as one of the acetylated starches, casein, or glue or other material may be added before the latex. After the rubber has been coagulated on the fibre, the latter is made into paper in the usual way, a 120 inch Scylinder machine be- I ing quite satisfactory. An artificial latex may be used instead of the natural rubber latex. The deposition of the rubber on the fibre may be carried out, if desired, as a continuous process, in which case the coagulant is added slowly but continuously.

The rubber-containing paper above described and from .020" to .025 in thickness has a tensile strength of 20004000 lbs. per sq. in., and gives a Mullen test of 200-300. Its tear resistance by the Elmendorf method is over 1400 in one direction and .1200 in a direction at right angles thereto. Ordinary paper seldom, shows a tear resistance above 80.0. Rope paper made from fibre cooked in the customary way has a tear resistance of about 600, but may show a higher tensile strength and Mullen test than paper made according to the above example. However, tensile strength and Mullen test are not the only properties which are being sought in the present invention. The tear resistance of the product made as above described is over 100% higher than the optimum for rope paper and shows appreciable improvement over some fabrics such as those used in the abrasive industry. .Also the resistance to ply 1 separation for paper made on a cylinder machine is increased by the present invention to at least 150% more than any paper heretofore made for this purpose. The resistance to ply separation is "determined according to:

the method which is the standard employed in the abrasive industry.

The methods of cooking the fibre as hitherto practiced have made use of lime, caustic soda and bleaching powder as chemical means to remove non-cellulosic material. If the fibre be cooked with lime there is the attendant difficulty of washing out the final traces of lime and at the same time the fibre is left in a hard harsh state well nigh useless from the commercial standpoint in the manufacture of saturating paper. Caustic soda has the property of rapidly removing waxes, fat, etc. from cotton fibre, but is severe in its action upon the strength of the fibres unless the cooking condition is rigidly controlled. Bleaching powder has not proven satisfactory except in the manufacture of certain types of paper. In general, the result of the ordinary cooking processes as now applied in the paper industry is a nice looking fibre which is quite satisfactory for the regular manufacture of paper but is of little value in the preparation of industrial papers because of its low stren h and low resistance to tear. If a cotton fi re be cooked for a long time and made into paper, its absorptive power is increased proportionately, but after a certain period, the tear strength, tensile and Mullen test will decrease, although the pliabilityof the fibrous product increases. Conversely, a short cooking gives a lower absorptive power and pliability, but higher tear resistance, tensile strength and Mullen test. By varying the time of cooking and blending the products of different periods of cooking intermediate properties can be obtained as desired.

Sheet materials made according to the pres ent invention lend themselves to all sorts of use but are more particularly valuable as I rubber, say up to 12%. The embossing qualities are also superior in most cases to those of fabric because there are no weave marks to show through, thus permitting the use of thinner pyroxylin etc., coatings, thereby giving greater flexibility in the finished material.

This material also lends itself to the manufacture of imitation leathers for deck materials for automobiles etc., and for general upholstery and covering purposes of various kinds, since it is moldable to some extent and can therefore be stretched around corners without wrinkling.

Rubberized sheet materials subject of this application have been found to give very pliable and strong abrasive products andaro stronger and more satisfactory in every way than materials now in use. a v

-.The properties of the sheets made from rubberized cotton fibres for any one of the above methods depend entirely on the method of cooking or removing the foreign materials from the surface of the fibre before rubberizing. If uncooked or raw cotton fibre is used in the process the resulting sheet containing from 10 to 12% rubber is very strong but is stiff and harsh.

There is a progressive increase in strength with the additions of rubber from 10 to 20% using raw cotton. Above 20% the addition of rubber while satisfactory from the standpoint of the sheet being free from spots of rubber not combined with fibre, still does not show increases in strength and pliability proportional to the added cost of the material.

cooking process to prevent overcooking thereby weakening the strength-of the cotton fibre.

If the cotton fibre is cooked too much sheets made therefrom and containing 33%% rubber have little or no strength, and to all outward appearances the rubber has been so completely absorbed by the fibre that a superficial examination oftheifinished product by one not skilled in the art would appear to warrant a conclusion that no rubber was present. In the ordinary paper-making products very little if any cotton is used except in the form of waste rags or other woven fabrics and the object of the cooking process in preparing these fibres for ordinary papers is to remove inks, dyes and other foreign material, and at the same time weakening the fibre to such an extent that it can be easily. handled in the beater and so that it will give a close and compact formation on the paper machine. The method of cooking hereinafter described is not new in the art of paper making, but by the very careful control of the conditions of cooking as herein described, fibres can be prepared which when combined with rubber from latex give a series of products suitable for the purposes described above which have never before been attained in paper making products.

According to the present invention, it ishusks and hulls goes hand in hand with the retention of fibre strength, for toremove the possible to utilize raw linter which contains husksa prolonged cooking is requiredwwith subsequent loss of strength in the fibres. Filling materials, colors and vulcanizing ingredients may be added to the contents of the beater. It may be desirable for some purposes to use a blend of paper making materials, that is to add wood pulp or other paper-stocks together with the cotton fibre.

By using the fibre cooked as above described and mixed about 10% of rubber as latex, a sheet material may be formed which is comparatively open in texture and which has the property of readily absorbing an adhesive. This type of sheet is especially suitable as a backing for waterproof varnishes -and coatings, cellulosic varnishes, lacquers, pyroxylin varnishes, fabrics and other coatings, and the sheet lends itself beautifully to embossing. Paper has heretofore been made for embossing purposes, but the paper is without strength. Rubbermay be added to paper pulp cooked in the ordinary way in order to ring up the stren 1th, but according to the present invention fibrecooked as above described may be mixed with 10% of rubber and paper made which is the full equivalent in strength of ordinary paper containing twice as much rubber. Furthermore it embosses more easily. By increasing the amount of rubber the depth of embossing may be increased without endangering breakage in the paper. All of the well-known types of embossing can be applied to such paper if the proportion of rubber be varied between the approximate limits of 5% and 20%. Paper containing the latter percentage of rubber may be embossed safely to a depth of inch without causing the paper to crack.

The amount of rubber added to the beater in the previous example may be increased to or as high as 100%, and the rubberfibre mixture can still be handled in the beater and formed into sheets on certain types of machines, such as leather board machines. With the higher percentages of rubber, machines of the Fourdrinier type are not recommended. The mixture of rubber and cooked cotton fibre described herein may readily be formed into a sheet. Its properties are such that it can be used with great satisfaction in various manufacturing arts, for example, as a soling material for shoes. The abrasion value of the sheeted product is increased by the additionof rubber, and this increase is more apparent the higher the concentration of rubber. Vulcanizing ingredients may be incorporated, and the sheet of material vulcanized as desired.

Another type of flexible product may be made in which various paper making ingredientsmay be included. For example, 15% of rubber is a suitable amount to be added, and together with the rubber not more than 2% of sodium silicate and 1% of rosin size are added to the beater. Other materials may be substituted for the sodium slicate and. rosin if desired, and the proportion of rubber may be varied, but the above proportions produce a satisfactory product.

The term rubber latex as employed in the specification and claims includes the natural rubber latex as it is obtained from the trees with or without a preservative, and it also includes rubber latex made artificially by dispersing raw rubber, vulcanized rubber, or reclaimed rubber in a dispersion medium such as water or other liquid which is not a solvent for therubber. The term also comprehends mixtures of natural rubber latex and artificial rubber latex of any sort, with or without compounding ingredients, vulcanizing agents, or agencies and colors.

While the invention is not limited to any particular method of preparing an artificial aqueous dispersion of rubber, or artificial dispersion of rubber in another dispersion medium, a suitable artificial latex may be 'inade by masticating rubber in a mixture containing the water and a protective colloid pulp which has been freed in whole or in part of fats, waxes, and/or other non-cellulosic material.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. A process for making a tear resisting sheet material from paper making fibre including cotton, which comprises cooking the fibre with an alkali at approximately 227 F. for 1 hrs, washing, beating, incorporating a water dispersion of rubber therewith in the presence of a protective colloid, and depositing the rubber on the fibre and forming into sheets.

2. A process for making a tear resisting sheet material from cotton fibre which comprises treating cotton fibre with sodium carbonate to remove fats, waxes, and other noncellulosic material at a proximately 227 F. for 1 hrs, washing, heating, adding rubber latex thereto, in the presence of a protective colloid, depositing the rubber on the fibre, and forming into sheets.

3. A process for making a tear resisting sheet material from paper making fibre, in-

cluding cotton fibre, which comprises treating cotton fibre with alkali carbonate at approximately 227 F. for less than 2 hrs. to remove fats, waxes and other non-cellulosic material, washing, combining with other 1 paper making fibre and beating, adding a water dispersion of rubber thereto, depositing the rubber on the fibre, and forming into sheets.

4. A process for making a tear resisting 1 sheet material from paper making fibre, including cotton fibre, which comprises treat ing cotton fibre, with sodium carbonate at approximately 227 F. for less than 2 hrs. to remove fats, waxes and other non-cellulosic material, washing, combining with other paper making fibre and beating, adding rubber latex thereto in the presence of a protective colloid, depositing the rubber on the 1 1% hrs. to remove fats, waxes and other nonface, said s pyroxylin.

cellulosic material, washing, beating, adding a water dispersion of rubber thereto, depositing the rubber on the fibre, forming into sheets, embossing and subsequently coating with a Waterproof varnish.

8. Process of making an embossed shee material which comprises treating paper making fibre with an alkali carbonate at approximately 227 F. for 1 h rs., washing, beating, incorporating a rubber latex there-' with in the presence of a protective vcolloid,

depositing the rubber on the fibre, forming into sheets, embossing, and subsequently coating with a cellul'osic waterproof varnish.

9. A process for making an embossed sheet material from paper making fibre including cotton fibre whichcomprises treating the cotton fibre with sodium carbonate at approximately 227 F. for approximately 1 hrs., washing, combining with other paper maln'ng fibre, beating, adding rubber latex thereto, depositing the rubber on the fibre,-

forming into sheets, embossing, and subse-' quently coating with a pyroxylin varnish.-

10. A process for making an embossed sheet material from paper making fibreineluding cotton fibre which comprises treating the cotton fibre with sodium carbonate at approximately 227 F. for approximately 1 hrs, washing, combining with other paper making fibre, beating, adding rubber latex thereto in the presence of a protective colloid, depositing the rubberon the fibre, forming into sheets, embossing, and subsequently coatin with a pyroxylin varnish.

11. s an article of manufacture, a'paper making fibre. deprived of water repellant waxes and other non-cellulosic material, the fibres being individually coated and bound together by a deposit from an aqueous dispersion of rubber, and superficially coated with a waterproof varnish. i

12. A sheet material comprising dewaxed cotton fibres individually coated and united by a deposit from rubber latex, and having a tear resistance of upwards of 1500, and a superficial coating of pyroxylin.

13. A sheet material comprising dewaxed cotton fibres individually coated and united by a deposit from an' aqueous dispersion of rubber, and having a tear resistance in excess of 800, a resistance to ply se aration at least 50% greater than rubber ree paper, deeply impressionable without rupture, said sheet material being coated superficially with pyroxylin.

14. Asa new sheet material paper, the

fibres of which are dewa xed and individually coated and united by an acetylated starc and a deposit from an aqueous dispersion of rubber, said paper having high tensile strength, tear resistance in excess of 800 igh flexibility, capable of receiving and ding dee impressions,an absorbent sur 15. As a new sheet material rubber treated sheet, "said sheet comprising dewaxed vegetable fibres individually coated and united by a-protective colloid, and a deposit'from rubber latex and said sheet having ,high tensile strength, atearresistance upwards, of 1500, ,a highly impressionable :absorbent surfacefflexible, haying alresistance to ply separation from 50+150% greater than similar rubber free sheets,-and coated with a pyrozylin varnish. I

gned at New York',- coui1tyand State of New York, this 23rd day of May 1928.

a REED P. hosE. Signed at New York, county of New York,

State of New York, this 24th dayof May, 1928. i

a HAROLD E. coma.

"nos

et material being coated with 80 

